It is known that polyacrylates, including polyurethane polyacrylates, can be cured using electron beam radiation. However, when the electron beam-cured films have a tensile strength greater than about 5,000 psi., they tend to be brittle and break before they elongate 100% of their initial length. When the electron beam-cured films are sufficiently extensible to avoid breaking until after they stretch 100%, then they tend to be weak and unable to resist tensile forces greater than 5,000 psi. Moreover, when strength and elongation are usefully combined, the cured films will frequently lack high modulus, and it is preferred to provide films having a tensile modulus in excess of 50,000 and a rupture energy in excess of 10,000 inch pounds per cubic inch. It is particularly desired to combine a tensile strength in excess of about 5,000 psi. with an elongation in excess of 200% and a rupture energy in excess of 10,000 inch pounds per cubic inch since this combination is especially effective in providing iron oxide-pigmented coatings for magnetic media.
The properties referred to above are measured on an electron beam-cured unpigmented free film having a thickness of about 1 mil.